It is sometimes desirable to apply a linear force using a spring or other source of energy and convert that force into a rotational force. For example, emergency actuators are often spring-powered to close a valve or actuate other equipment in an emergency situation when the normal source of power used to operate the valve or equipment is lost, whether that source of power be hydraulic, electrical, or otherwise. A typical emergency valve actuator, used with a fuel line valve and operated by hydraulic fluid pressure, will be driven by a spring to close the valve, in case hydraulic pressure is lost, in order to avoid fuel leaks. One such actuator is described in U.S. Pat. No. 5,027,667.
In other situations, it is desirable to operate valves and other equipment using a simple linear piston-and-cylinder drive arrangement such as provided by a rotary helical actuator. Such an actuator typically uses a cylindrical body with an elongated rotary output shaft extending coaxially within the body. An end portion of the shaft provides the drive output. An elongated annular piston sleeve has a sleeve portion splined to cooperate with corresponding splines on a ring gear attached to the sidewall of the body and on the output shaft exterior. The piston sleeve is reciprocally mounted within the body and has a head for the application of fluid pressure to one or the other opposing sides thereof to produce axial movement of the piston sleeve. In lieu of splines, force can be transmitted between the piston sleeve and the body and the output shaft using balls or rollers.
As the piston sleeve linearly reciprocates in an axial direction within the body, the outer splines of the sleeve portion engage the splines of the ring gear to cause rotation of the sleeve portion. The resulting linear and rotational movement of the sleeve portion is transmitted through the inner splines of the sleeve portion to the splines of the shaft to cause the shaft to rotate. Bearings are typically supplied to rotatably support one or both ends of the shaft relative to the body, and to prevent longitudinal movement of the shaft.
When using such actuators to operate valves and other equipment, it is often desired to provide an indication of the rotational position of the shaft, and hence the valve or equipment to which it is connected. This can be achieved through a visual mechanical indicator mounted on the actuator shaft itself or a remote electronic display that requires an electrical signal indicative of the rotational position of the shaft. For example, a pair of microswitches are sometimes mounted on emergency fuel valve actuators in position so that one is actuated when the actuator shaft is in a rotary position corresponding to the fuel valve it operates being in an open position. The other microswitch is positioned so that it is actuated when the actuator shaft is in a rotary position corresponding to the fuel valve being in a closed position, such as occurs when the actuator is operated to close the fuel valve in an emergency situation.
The electrical signals generated by the actuation of the electronic microswitches are conveyed to a remote electronic display so that the status of that fuel valve as well as all other fuel valves in a widely distributed system can be remotely monitored by a human attendant. Of course, the signals can also be monitored by a computer to record operational data and automatically take appropriate responsive action. The generally same situation exists when an actuator is used to control other type valves and equipment.
It is critical to the reliability of the system that the electronic microswitches mounted on the actuator be protected from the environment and also from the hydraulic fluid used as the medium to operate many rotary helical actuators. Often, such actuators are mounted outdoors exposed to the elements, or if indoors, in dirty environments such as factories, warehouses and sheds where environmental contaminants can result in failure of the electronic microswitches. The presence of high pressure hydraulic fluid used to operate the actuator can also lead to contamination of the electronic microswitches and their failure. Finally, when in such environments, physical contact by equipment, workmen or work material can also damage the relatively delicate microswitches.
It is also often required on such actuators to provide a means for adjusting the end limit of rotation of the actuator shaft, while the actuator is attached to the valve or other equipment it controls. This adjustment is needed so that when the actuator shaft is rotated fully in one rotational direction where it is intended, for example, to fully close a valve, the valve will, in fact, be fully closed. It is desirable that the adjustment be accomplished with an easy and quick manual adjustment using conventional tools without requiring removal or even loosening and rotation of the actuator body from its mounting or the actuator shaft from the valve. As with the electronic microswitches it is desirable to protect this adjustment mechanism from contamination and physical contact that could damage the mechanism.
The present invention solves all of these problems while providing electronic rotational position sensors for the actuator shaft and an end limit of rotation adjustment mechanism for the shaft. The invention provides other related advantages.